The disclosure of Japanese Patent Application No. 11-368521 filed on Dec. 24, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a rubber component that provides a fuel seal, which is used as a sealing member, such as an O-ring, a packing or a gasket, for preventing leakage of fuel or fuel vapors in a fuel tank or a fuel supply system for vehicles, or used as a diaphragm or the like that operates in fuel or fuel vapors.
2. Discussion of Related Art
Fuel vapors leaking out into the atmosphere from a vehicular fuel system may cause air pollution, and therefore restrictions are imposed on the emission of such fuel vapors. For example, fuel vapors emitted from a fuel tank are adsorbed by an adsorbent contained in a canister, and sucked under vacuum into an intake pipe during operation of the engine, together with the outside air admitted through an air inlet of the canister. The fuel vapors and the air thus introduced into the intake pipe are then supplied to and burned in a combustion chamber of the engine. The canister is held in communication with the outside air, or the ambient atmosphere, and a control valve for adjusting the pressure in the fuel tank is provided between the tank and the canister.
In the above-described evaporative emission control system for preventing fuel vapors from being discharged into the atmosphere, a breather line communicating with the canister and an internal pressure control line for regulating the pressure in the fuel tank are provided with various control components. In this system, a reliable seal needs to be proviced at mounting portions of these components so that fuel vapors are prevented from leaking into the atmosphere through the mounting portions.
Fuel vapors may also leak from mounting portions of various components provided in any type of fuel system as well as the above evaporative emission control system, and therefore a secure seal needs to be provided at the mounting portions. The leakage of fuel vapors is prevented not only with sealing members, such as an O-ring, a packing and a gasket, provided at mounting portions of these components, but also with diaphragms used in various types of control valves that are opened and closed with various kinds of pressures applied thereto in response to an external control signal. In such a control valve, the diaphragm is used to support the valve for smooth operation thereof, such that the diaphragm prevents fuel vapors present inside of the diaphragm from leaking out into the atmosphere outside of the diaphragm.
As described above, the sealing members, such as an O-ring, packing and a gasket, or diaphragms operating in fuel and fuel vapors are used in stationary or fixed portions, or internal operating portions, of various types of components used in the fuel system of the vehicle. Both the sealing members and the diaphragms are required to provide a reliable or secure seal so as to prevent fuel and fuel vapors inside the fuel system from leaking out of the system. Depending upon the usage and environments of use, the sealing members and the diaphragms are required to exhibit various characteristics, such as heat resistance, oil resistance, elasticity or flexibility, and gas impermeability, and to reliably maintain its sealing function for a long period of time.
To this end, rubber, such as epichlorohydrin rubber or fluorosilicon rubber, has been often used as a material for those components. However, the use of only these types of rubber does not give the resulting components with sufficient characteristics, such as gas impermeability. Especially when sour gasoline containing peroxides is used as fuel, carbon-to-carbon connections of hydrocarbon in the rubber material are broken, and the sealing members or diaphragms become soft and adhesive, and thus cannot provide sufficient sealing capabilities.
In view of the above problem, Japanese Patent No. HEI 4-27939, for example, discloses a technology of forming a diaphragm, using rubber whose main component is acrylonitrile-butadiene copolymer rubber (hereinafter referred to as xe2x80x9cNBRxe2x80x9d) . With this technology, the diaphragm is formed by subjecting the surface of the rubber material to chromic acid etching for increased adhesiveness, to thus form a processed layer on which a coating layer made of nylon resin is formed.
Although the NBR used as a rubber material in the above technology is relatively inexpensive, it is difficult to coat its surface with various types of layers. For example, there is a need to perform a process for increasing adhesiveness, such as etching with chromic acid as described above, that is suitable for a material coating the rubber. The reason why the chromic acid etching provides increased adhesiveness of nylon is not apparent from the above-identified patent publication. In fact, various processes were actually carried out, and the chromic acid etching was found to be effective to increase the adhesiveness, for the reason that was only presumed afterwards.
Thus, there has been a demand for such rubbers that exhibit the above-mentioned characteristics, and also can be easily coated at their surfaces with nylon for increasing adhesiveness.
In the meantime, fluoro rubber is known as a rubber material that allows permeation of only a small amount of gasoline vapors. However, fluoro rubber has disadvantages such as insufficient low-temperature characteristics and expensiveness.
It is therefore an object of the invention to provide a rubber component used as a fuel seal, which is excellent in the heat resistance, oil resistance, elasticity or flexibility and gas impermeability, which can reliably maintain its sealing function for a long period of time, and which can be easily manufactured at a reduced cost.
To accomplish the above object, a rubber component used as a fuel seal is provided according to the first aspect of the invention, which includes a base formed principally of fluorosilicon rubber, and a coating layer formed principally of nylon, the base being coated with the coating layer.
According to the second aspect of the invention, there is provided a rubber component that provides a fuel seal, which includes a base formed principally of fluorosilicon rubber, and a coating layer formed principally of a fluorine-contained resin, the base being coated with the coating layer.
According to the third aspect of the invention, there is provided a rubber component that provides a fuel seal, which includes a base formed principally of hydrin rubber, and a coating layer formed principally of nylon, the base being coated with the coating layer.
According to the fourth aspect of the invention, there is provided a rubber component that provides a fuel seal, which includes a base formed principally of hydrin rubber, and a coating layer formed principally of a fluorine-contained resin, the base being coated with the coating layer.